Telephone system



PATENTED AUG. 25, 1908. H. G. WEBSTER.

TELEPHONE SYSTEM.

APPLIUATION TILED FEB. 10, 1906.

THE NORRIS PETERS cc., wasmuorou, n. c.

UNITED sTATnsPATEnT onnronf.

HARRY G. WEBSTER, OF CHICAGO, ILLINOIS, ASSIGNOR TO'MILO G. KELLOGG, OFCHICAGO,

. ILLINOIS.

TELEPHONE SYSTEM.

Application filed February 10, 1906.

systems generally and more particularly to the arrangement of linecircuits and associated apparatus, by which the usual signals aretransmitted and controlled by the subscriber and operator.

The principal object of the invention is to provide a novel organizationof circuits and apparatus for accomplishing these functions, which shallbe simple in construction, efficient in operation and economical to manufacture.

In carrying out my invention, I employ,

in association with the telephone line circuit,

a novel controlling relay of the so-called double acting type. Thisdouble acting relay, which is along the line of those disclosed by me inprior applications, is arranged to cause the display of a line signal inresponse to a given energization, and to efface said signal in responseto a different energization. This is preferably brought about byarranging the relay contacts so that they will be moved through aportion of their maximum range in response to a lesser energization ofthe relay, and through the remainder of their range in response to agreater energization-the former to light a lamp, and the latter toextinguish it. In addition to these functions, the relay also varies theconnections to its windings and to a resistance which cooperates withit. In the cord circuit, I also preferably employa relay of the doubleacting type for controlling the display and effacement ofthe usualsupervisory signal.

The nature and objects of the invention will more fully appear from thefollowing detailed description, taken in connection with theaccompanying drawing, and the scope of the invention will beparticularly indicatedin the appended claims.

In the drawing, which illustrates diagrammatically a telephone systemconstructed in accordance with the present invention, A and B designatetwo substations which are connected to a central office C by suitabletelephone lines. The equipment at substation Specification of LettersPatent.

Patented Aug. 25, 1908.

Serial No. 300,448.

A, which may be of any preferred type, is here shown as comprising acall-bell 1 in series with a condenser 2, normally included in bridge ofthe telephone line limbs 34 by the engagement of the switch-hook 5 withthe contact 6. A second normally open bridge, including the transmitter7 and receiver 8, is closed at the contact 9 by the switch-hook 5whenever the receiver is removed therefrom. At the central office, theline limbs are extended in the usual manner to a source of current andto the contacts 9 and 10 of multiple jacks 11. A double acting relay 12,which is employed in the control of the line signal 13, here shown as anincandescent lamp, comprises a winding 14 normally in cluded in a branch15 which, together with a conductor 16, relay contacts 1718, and aconductor 19, normally extends the line limb 3 to the live pole of thebattery 20. A contact 21 and its connecting conductor 22 co operate withthe movable contact 18 and its conductor 19 to short circuit aresistance 23, which is normally included in the line limb 3, or itsextension to the ack contact 9. The relay 12 is also provided with awinding 24 which is included in a branch 25, by which the line limb 4 isextended to the conductor 26 and the grounded side of the battery 20.Thewinding 24 is normally short cii'cuited through the agency of thefixed contacts 27 and 28, which are res ectively connected by theconductors 29 an 30 to the conductor 25 and the line limb 4, and acooperating contact 30*, which is normally held in engagement with thefixed contacts by a spring 31.

The movable contact 30 is adapted to be 7 drawn out of engagement withthe fixed contacts 2728 by a second movable contact 32, which ispermanently connected to the live conductor 16 by a conductor 33, whichincludes the signal lamp 13 in circuit.

The equipment and the connections thus far described with reference tosubstation A are practically duplicated in connection with substationB,and the corresponding parts are indicated, in connection with the latterstation, by similar primed characters.

At the central oflice, the means for connecting subscribers lines forconversation comprises an answering plug 34, whose tip contact 35 isconnected by strands 36 and 37 to the ti contact 38 of a calling plug39, and whose s eeve contact 40 is connected by strands 41 and 42 to thesleeve contact 43 of the calling plug 39. The strands 36 and 37 on theone hand, and 41 and 42 on the other, are separated by the usualcondensers 44 and 45 respectively. A conductor 46 is permanentlyconnected by a lead 47 to the live pole of the battery 20, while asecond conductor 48 is normally maintained at the potential of ground bythe lead 49, connecting it to the grounded side of the battery. Thesupervisory signal lamp 50, associated with the answering end of thelink-circuit, is included in a bridge 51 between the conductors 46 and48, which is adapted to be made and broken by the contacts 52, 53 and540i a double acting relay 55, whose winding 56, is included in a branch57 between the strand 36 and the grounded conductor 48 and whose winding58 is included in a like branch 59 between the strand 41 and the liveconductor 46. A similar supervisory lamp 50 is asso ciated with thecalling plug 39. This lamp is included in a bridge 51 between theconductors 46 and 48, which is similarly made and broken by the contacts52, 53 and 54 of a similar supervisory relay 55, Whose winding 56 isincluded in abranch 57 between the strand 37 and the grounded conductor48; and whose winding 58 is included in a branch 59 between the strand42 and the live conductor 46.

The strands 37 and 42 of the calling end of the link-circuit areconnected to the usual listening-key levers 6061, which may be depressedinto engagement with the contacts 6263 to close a bridge between thestrands including a condenser 64, the secondary winding of an inductioncoil 65 and the operators receiver 66. The operators transmitter 67 isincluded in a local circuit with the primary Winding of the inductioncoil 65 and the battery 68. These strands are also provided with theusual ringing key levers 69, 70, which normally engage the fixedcontacts 71 and 72 to maintain the continuity of the strands 37 and 42,but which are adapted to be moved into engagement with the contacts 73and 74 on the one hand to connect the sleeve strand 42 to the live poleof the battery 20 through the conductor 75, which includes a protectiveresistance 76; and on the other hand, to connect the tip strand 37 tothe grounded branch 77, which includes the generator 78 and theresistance lamp 79.

In the operation of the system, a party at substation A, desiring toconverse with a party at substation B, removes his receiver 8 from itsswitch-hook 5 so as to allow the latter to complete the normally openbridge be tween the telephone line limbs 3 and 4. Since the oppositepoles of the battery 20 are normally connected to the line limbs 3 and4, the closing of the bridge at the substation will complete a circuitthrough resistance 23 and the winding 14 of the relay 12, therebysu'lficiently energizing it to move its contact 32 into engagement withits contact 30 to complete the bridge through the signallamp 1.3 tocause its display, as an indication to the operator that a connection isdesired. The circuit, closed in this manner by the removal of thereceiver 8 at the substation A, may be traced as follows: from the livepole of the battery 20, through the conductor 16, the conductor 15including the winding 14 of the relay 12, relay contacts 17-18,conductor 19, resistance 23, line limb 3, switch-hook 5, contact 9,receiver 8 and transmitter 7, line limb 4, the short circuitingconnection including conductors 29 and 30 and contacts 27, 28 and 30,and conductors 25 and 26 to the grounded side of the battery. Uponobserving the signal displayed in response to the closure of thiscircuit, the operator will insert the answering plug 34 into theanswering ack of the line 3-4 and depress the listening key 60-61 toconnect her receiver 66 in circuit with the substation to learn thewishes of the calling party. The insertion of the plug 34 into theanswering jack will close a circuit from the live pole of the battery20, through the conductor 16, the conductor 15 including the winding 14of the relay 12, contacts 17, 18, conductor 19, a portion of theextended line limb 3, jack contact 9, tip contact 35, strand 36, branch57 including the winding 56 of the supervisory relay 55, to thegrounded. conductor 48. The closing of this circuit will energize therelay 12 sufficiently to bring the contacts 18 and 21 into engagement,thereby breaking the circuit just traced and short circuiting theresistance 23. At the same time, however, the contact 32 is attractedwith sufiicient force to carry the contact 30 out of engagement with itsfixed contacts 27 and 28, thereby removing the short circuit from aboutthe winding 24 of the relay 12 and permitting the latter to be energizedover a new path sufficiently to maintain the parts in their attractedpositions. The path through the second winding 24 may be traced from thelive pole of the battery 20, through the conductors 4746, the branch 59including the winding 58 of the supervisory relay 55, strand 41, plugcontact 40, jack contact 10, the conductor 25 including the winding 24,to the grounded 'side of the battery 20. In addition to providing thispath for current through the second winding 24, the attraction of thecontact 32 will break the bridge including the signal lamp 13 at thecontacts 27 and 30, thereby causing the ei'lacement of the call signal.

As soon as the contacts of the relay 12 have been moved into their finalpositions, a path for current from the jack contact 10 to the grounded.side of the battery 20, in addition to that through the winding 24 ofthe cut-off relay, will be provided as follows: over the line limb 4,through the closed bridge at the substation, line limb 3, around theresistance 23 by Way of the short circuiting path including theconductor 22, contacts 21-18 and conductor 19, jack contact 5 9, plugcontact 35, strand 36, branch 57 including the Winding 56 of thesupervisory re lay 55, to the grounded conductor 48. By reason of thefact that both of these paths for current are closed, the supervisoryrelay 55 will be sufficiently energized to cause the separation of thecontacts 53 and 54, thereby breaking the bridge 51 through the signallamp 50 and preventing its display. However, if the path through thesubstation is 1 5 broken, the resulting energization Will be sufficientonly to maintain the contacts 52 and 53 in engagement, but not toseparate the contacts 53 and 54. Thus, if the subscriber returns thereceiver 8 to its hook, the bridge through the supervisory lamp 50 Willbe closed and the lamp Will be lighted, as an in dication of thesubscribers act.

Upon depressing the listening key 6061 and learning that the callingparty desires connection with the line 34, the operator will touch thetip contact 38 of her plug 39 against the ack contact 10 to determinethe busy or idle condition of theline. From the circuits previouslytraced, it Will be seen that if the line 3 4 is in use, a potentialabove that of ground Will exist at the testing contact 10; and as soonas the contact 38 is touched to it, there Will be an instantaneous flowof current from the tip 38 through the strand 37, branch 57 to thegrounded con ductor 48. This Will vary the charge on the condenser 64,resulting from the initial closure of the listening key 60*61, and willpro- 'd'uce a click in the operators receiver 66,

40 thus indicating to her the busy condition of the line. If the line isfound to be idle, the operator will insert the plug 39 into the jack 11,thereby momentarily closing a circuit through the Winding 14 of therelay 12 to completely actuate its contacts in a manner previouslydescribed in connection With the relay 12. This Will immediately removethe call-signal 13 from the control of the party at substation B, shortcircuit the resistance 23, and substitute the Winding 24 for the Winding14 as the energizing medium for re taining the relay contacts in theirattracted positions. At this time, the only circuit through thesupervisory relay Will be that 55 through its Winding 58. This, aspreviously indicated, Will be suflicient to bring its con.- tacts 5253into engagement, Without separating the contacts 5354, and Will thuscomplete the bridge through the lamp 50,

60 causing its display. This lamp Will remain lighted until the normallyopen bridge at the substation B is closed by the removal of the receiver8 from its switch-hook 5. The

closing of this bridge will complete the alterthrough the substation andthe Winding 56 of the supervisory relay 55, thereby increas ing theenergization of said relay sufliciently to break the bridge of the lamp50 at the relay contacts 5354, as an indication to the operator that thecalled party has an swered.

In ringing the party at substation B, the operator-depresses the ringingkey 6970, thereby connecting the sleeve strand 42 of the link-circuitWith the live pole of the battery through the protective resistance 76,so

as to continue the supply of battery current to the Winding 24 of therelay 12. At the same time, ringing current Will be applied. to the tipstrand 37 and thence out over the line limb 4, through the bell 1 andcondenser 2 at the substation, back over the line limb 3 to ground,either by Way of the Winding 24 and the conductors 2526, or by Way ofthe the sleeve strand 42, the conductors 7 516, and the battery 20. Withthe parties thus connected, the supervisory lamps 50 and 50 Will remaindark during conversation. soon as either party finishes his conversationand hangs up his receiver, the circuit through the lesser energizingWindingof the supervisory relay, corresponding to his line, Will bebroken, and the bridge through the lamp completed by the engagement ofthe relay contacts. The lighting of both lamps Will be a signal to theoperator to disconnect the lines. It Will also be observed that, Withthe parties thus connected, the resistances 23 and 23 are not includedin the talking circuit, and that the latter is properly balanced by thearrangement of the windings of the line relays.

Obviously, in carrying out my invention, the batteries 20 and 68 may beone and the same, the various ground connections may be replaced by acommon return, and other alterations and modifications may be madeWithout departing from the spirit and scope of my invention. I,therefore, do not Wish to be limited to the specific matter illustrated,but aim to cover, by the terms of the appended claims, all suchalterations and modifications.

What I claim as new, and desire to secure by Letters Patent of theUnited States, is

1. A telephone system comprising a telephone line conductively uniting asubstation With a jack at the central office, a link-circuit, aconnecting plug adapted to be inserted into said jack to connect saidline and link-circuit, means for holding conversation over said line andlink-circuit, a resistance normally included in said line, a controllingelectro-magnet associated With said line at the central oflice, meansunder the control of the subscriber for energizing said magnet byclosing a circuit through said resistance, means under the control ofthe operator for modifying said energization, and means actuated by thelatter energization to close a short circuit about said resistance.

2. A telephone system comprising a telephone line conductively uniting asubstation with a jack at the central oflice, a linkcircuit, aconnecting plug adapted to be inserted into said jack to connect saidline and link-circuit, means for holding conversation over said line andlink-circuit, a resistance normally included in said line, electricallyoperated signaling apparatus associated with said line at the centraloffice, means under the control of the subscriber for actuating' saidapparatus to cause the display of a signal by closing a circuit throughsaid resistance, means under the control of the operator for actuatingsaid apparatus to eflace said signal, and means actuated therewith toclose a short circuit about said resistance.

3. A telephone system comprising a telephone line conductively uniting asubstation with a jack at the central office, a link-circuit, aconnecting plug adapted to be inserted into said jack to connect saidline and linkcircuit, means for holding conversation over said line andlinkcircuit, a resistance nor mally included in said line, a call'signalassociated with said line at the central office, a controllingelectro-magnet for said signal, means under the control of thesubscriber for energizing said electro-magnet by supplying current overa path through said resistance and a winding of said magnet, means underthe control of the operator for modifying the said energization of saidelectromagnet, and means responsive to the former energization todisplay said signal and to the latter energization to efface said signaland to close a short circuit about said resistance.

4. A telephone system comprising a telephone line conductively uniting asubstation with a jack at the central oflice, a link-circuit, aconnecting plug adapted to be inserted into said jack to connect saidline and link-circuit, means for holding conversation over said line andlink-circuit, a resistance normally included in said line, a call signalassociated with saidline at the central office, a controllingelectromagnet for said. signal, means under the control of thesubscriber for energizing said electro-magnet by supplying current overa path through said resistance and a winding of said magnet, means underthe control of the operator for increasing the said energization of saidelectromagnet, and means responsive to the former energization todisplay said signal and to the latter ener gization to eiiace saidsignal and to close a short circuit about said resistance.

5. A telephone system comprising a telephone line extending from asubstation to a central office, a link-circuit for making con nection tosaid line, means for holding conversation over said line andlink-circuit, a resistance normally included in said line. a call signalassociated with said line at the central A office, a controllingelectromagnet for said signal, means under the control of the subscriberfor energizing said electromagnet by supplying current over a paththrough said resistance and a winding of said magnet, means under thecontrol of the operator for increasing the energization of said magnetby supplying current over a second path through the same magnet winding,and means responsive to the said former energizationto display saidsignal and to the latter energization to eflace said signal and to closea short circuit about said resistance.

6. A telephone system comprising a telephone line conductively uniting asubstation with a jack at the central office, a link circuit, aconnecting plug adapted to be inserted into the said jack to connectsaid line and link-circuit, means for holding conversation over saidline and link-circuit, a resistance normally included in said line, acall signal associated with said line at the central office, acontrolling electromagnet for said signal, means under the control ofthe subscriber for energizing said electromagnet by supplying currentover a path through said resistance and a Winding of said magnet, meansunder the control of the operator for increasing the energization ofsaid magnet by supplying current over a second path through the samemagnet winding, and means responsive to the said former energization todisplay said signal and to the latter energization to efface said signaland to close a short circuit about said resistance.

7. A telephone system comprising a telephone line extending from asubstation to. a central oflice, a link-circuit for making connection tosaid line, means for holding eonversation over said line andlink-circuit, a controlling electro-magnet having two windingsassociated with said line at the central oliice, means under the controlof the subscriber for energizing said magnet, means under the control ofthe operator for modifying the energization of said magnet by supplyingcurrent over a path through one of said magnet windings, and meansresponsive to the modified energization to change said path of currentsupply to exclude said. one magnet winding and include the other.

8. A telephone system comprising a telephone line extending from asubstation to a central oflice, a link-circuit for making connection tosaid line, means for holding conversation over said line andlink-circuit, a controlling electromagnet having two windings associatedwith said line at the central office, means under the control of thesubscriber for energizing said electromagnet by supplying current over apath through one of said magnet windings, means under the control of theoperator for modifying the energization of said magnet by supplyingcurrent over a second path through the same magnet winding, and meansresponsive to the modified energization to change said second path toexclude said magnet Winding and to include the other magnet winding.

9. A telephone system comprising a tele phone line extending from asubstation to a central office, a link-circuit for making connection tosaid line, means for holding conversation over said line andlink-circuit, a call signal associated with said line at the centraloffice, a two-winding controlling magnet for said signal, means underthe control of the subscriber for energizing said magnet, means underthe control of the operator for modifying the energization of saidmagnet by supplying current over a path through one of said magnetwindings, and means responsive to the initial energization of saidmagnet to display said signal and to the modified energization to efiacesaid signal and to change said path of current supply to exclude saidone magnet winding and include the other.

10. A telephone system comprising a telephone line extending from asubstation to a central oflice, a link-circuit for making connection tosaid line, means for holding conversation over said line andlink-circuit, a-

call signal associated with said. line at the central office, a twowinding controlling electromagnet for said signal, means under thecontrol of the subscriber for energizing said electromagnet by supplyingcurrent over a path through one of said magnet windings, means under thecontrol of the operator for modifying the energization of said magnet bysupplying current over a second path through the same magnet winding,and means responsive to the initial energization of said magnet todisplay said signal and to the modified energization to efface saidsignal and to change said path to exclude said magnet winding and toinclude the other magnet winding.

11. A telephone system comprising a telephone line extending from asubstat on to a central office, a link-circuit for making connection tosaid line, means for holding conversation over said line andlink-circuit, a resistance normally included in said line, a call signalassociated with said line at the central office, a controllingelectro-mzignet for said signal having two energizing windings, meansunder the control of the subscriber for energizing said electro-magnetby supplying current over a path through one of said windings, meansunder the control of the operator for modifying said energization bysupplying current first to one of said windings and then to the other,and means responsive to the initial energization to display said signaland to the modified energization to efface said signal and close a shortcircuit about said resistance.

12. A telephone system-comprising a telephone line extending from asubstation to a central ofiice, a link-circuit for making connection tosaid line, means for holding conversation over said line andlink-circuit, a resistance normally included in said line, a call signalassociated with said line at the central office, a controllingelectro-magnet for said signal having two energizing windings, meansunder the control of the subscriber for energizing said electro-magnetby supplying current over a path through one of said windings, meansunder the control of the operator for increasing said energization bysupplying current first to one of said windings and then to the other,and means responsive to the initial energization to display said signaland to the increased energization to eflace said signal and close ashort circuit about said resistance.

13. A telephone system comprising a telephone line extending from asubstation to a central office, a link-circuit for making connection tosaid line, means for holding conversation over said line andlink-circuit, a resistance normally included in said line, a controllingelectromagnet associated with said line at the central oflice, meansunder the control of the subscriber for energizing said magnet, meansunder the control of the operator for modifying said energization bysupplying current over a definite path, and means responsive to thelatter energization to change said path and to short circuit saidresistance. v

14. A telephone system comprising a telephone line extending from asubstation to a central office, a link-circuit for making connection tosaid line, means for holding conversation over said lme andlink-circuit, a

resistance normally included in said line, a

two winding controlling electromagnet associated with said line at thecentral. oflice, means under the control of the subscriber forenergizing said magnet, means under the control of the operator formodifying the energization of said magnet by supplying current over apath through one of said magnet windings, and means responsive to themodified energization both to change said path of current supply toexclude said one magnet winding and include the other, and to shortcircuit said resistance.

15. A telephone system comprising a telephone line extending from asubstation to a central office, a link-circuit for making connection tosaid line, means for holding conversation over said line andlinkcircuit, a resistance normally included in said line, a two windingcontrolling electro-magnet associated with said line at the centraloifice, means under the control of the subscriber for energizing saidelectro-magnet by supplying current over a path through one of saidmagnet windings, means under the control of the operator for modifyingthe energization of said magnet by supplying current over a second paththrough the same magnet winding, and means responsive to the modifiedenergization both to change said path to exclude said magnet winding andinclude the other magnet winding, and to short circuit said resistance.

16. A telephone system comprising a telephone line extending fromasubstation to a central o'llice, a link-circuit for making con nectionto said line, means for holding con versation over said line andlink-circuit, a resistance normally included in said line, a two windingcontrolling electro-magnet associated with said line at the centraloilice, means under the control of the subscriber for energizing saidelectro-magnet by supplying current over a path through saidresistanceand one of said magnet windings, means under the control of" theoperator for modifying the en ergization of said magnet by supply ingcurrent over a second path through the same magnet winding, and meansresponsive to the modified energization both to change said path toexclude said magnet winding and include the other magnet winding, and toshort circuit said. resistance.

1.7. A telephone system comprising a telephone line extending from asubstation to a central ollice, a link-circuit for making connection tosaid line, means for holding conversation over said line and,link-circuit, a resistance normally included in said line, a call signalassociated with said line at the central oflice, a two windingcontrolling electromagnet for said signal, means under the control ofthe subscriber for energizing said electromagnet by supplying currentover a path through said resistance and one of said magnet windings,means under the control of the operator for modifying the energizationof said magnet by supplying current over a second path through the samemagnet winding, and means responsive to the initial energiza tion ofsaid magnet to display said signal and to the modified energization toeflace said signal, to change said path to exclude said magnet windingand include the other magnet winding, and to close a short circuit aboutsaidresistance.

18. A telephone system comprising a telephone line extending in twolimbs from a substation to a central oilice, a link-circuit for makingconnection to said line, means for holding conversation over said lineand link circuit, a resistance normally included in one limb of saidline, a source of current, a controlling electromagnet having two windins, means for including its windings in circuit between the poles of saidsource of current and said line limbs respectively, means forinterrupting one of these paths and short circuiting said resistance,means normally short circuiting the winding included in the other path,and means for removing said short cir= cuit.

19; A telephone system comprising a telephone line extending in twolimbs from a substationto a central office, a link-circuit for makingconnection to said line, means for holding conversation over said lineand link-circuit, a resistance normally included in said line, a callsignal associated with said lnie, a two winding electromagnet forcontrolling saidcall signal, means for including said windings incircuit between the poles of said source of current and said line limbsrespectively, means normally short circuiting one of said windings,means at the substation for bridging said line limbs to cause a limitedenergization of said electromagnet, means responsive thereto to displaysaid signal, means operative upon the connection of said link-circuit tosaid line to modify said energization, and means responsive to saidmodified energization to remove the short circuit about said winding toopenthe circuit of the other winding and to short circuit saidresistance.

20. A telephone system comprising a telephone line conductively unitinga substation with a jack at the central oflice, a link-circuit, aconnecting plug adapted to be inserted into said jack to connect saidline and link-circuit, means for holding conversation over said line andlink-circuit, a call signal apparatus associated with said line at thecentral oflice, a resistance independent of that of said call signalapparatus normally included in said line, means under the con trol ofthe subscriber for operating said apparatus by closing a circuit throughsaid resistance, supervisory apparatus associated with the link-circuit,and means under the control of the operator for modifying said callsignal apparatus by closing a circuit through said supervisory apparatusand means actuated thereby to close a short cir cuit about saidresistance.

21. A telephone system comprisinga telephone line extending in two limbsfrom a substation to a central oflice, a link-circuit for makingconnection to said line, means for holding conversation over said lineand link-circuit, a grounded source of current, a controlling relayhaving two energizing windings included on opposite sides of said sourcein bridge of said line limbs, a grounded branch connected from one linelimb through normal contacts of said relay, a resistance associated withthe other line limb, and means for cutting out said resistance when therelay operates.

22. A telephone system comprising a tele phone line extending in twolimbs from a substation to a central office, a linkcircuit for makingconnection to said line, means for holding conversation over said lineand link circuit, a grounded source of current, a con trolling relayhaving two energizing windings included on opposite sides of said sourcein bridge of said line limbs, a grounded branch connected from one linelimb through normal contacts of said relay, a resistance normallyincluded in the other line limb, and means for cutting out saidresistance when the relay operates.

23. A telephone system comprising a telephone line extending in twolimbs from a substation to a central office,'a link-circuit for makingconnection to said line, means for holding conversation over said lineand linkcircuit, a grounded source of current, a controlling relayhaving two energizing windings included on o posite sides of said sourcein bridge of said line limbs, a grounded branch connected from one linelimb through normal contacts of said relay, a resistance nor mallyincluded in the other line limb, a signal lamp connected in circuit withsaid source through normally open contacts of said relay, and means forcutting out said resistance when said relay operates.

' In witness whereof, I hereunto subscribe my name this 8th day of Feby,1906.

HARRY G. WEBSTER.

Witnesses:

A. H. DYsoN,

CAROLYN WEBER.

